In the past several years, various types of display technologies have continued to advance rapidly. These various types of display technologies include liquid crystal display (LCD), plasma display panel (PDP), organic electroluminescent or organic light emitting diode (OLED), electroluminescent display (EL), vacuum fluorescent display (VFD), field emission display (FED), etc. In particular, significant development efforts and dramatic improvements have been made in the area of flat panel display (FPD) technology. FPDs are thin, flat electronic display used for displaying various kinds of information and data including text, graphics, video, etc. While LCD is still considered one of the most mature and common flat panel display technologies, other types of flat panel display technologies including OLED have generated a great deal of interest and attracted a lot of attention in research, development, and application in recent years.
One of the methods for forming larger flat panel display from smaller display units is referred to as tiling. Individual display tiles or units are usually arranged in an array or a matrix format and attached to each other along the edges of the display tiles to form a single tiled flat panel display of larger size. One of the major problems encountered in forming larger FPDs by tiling is to hide or conceal the seams (gap) between the adjacent display tiles so that the final assembled FPD can be viewed as a seamless single display unit. One approach to solve this problem is to put a black matrix (also called black grid or opaque mask herein) on a cover plate (also referred to as the optical integration plate (OIP) herein) that aligns with the individual pixels on the display tiles. In addition, the black matrix can also be used to improve the display contrast and/or to prevent light leakage from adjacent display pixels. FIG. 1 illustrates a tiled flat panel display configuration/structure in which a plurality of display tiles 100A-D are arranged in a matrix format and attached to a common cover plate 110. As shown in FIG. 1, the cover plate 110 with a black grid or black matrix 115 is placed on top of the display tiles 100A-D. The black matrix 115 is aligned with the individual pixels disposed in the display tiles 100A-D. In this configuration, the black matrix is used to improve the contrast of the display and also to hide the seams 120 between the display tiles 100A-D. The display tiles 100A-D in FIG. 1 also may include a plurality of back panels 130A-D that are attached to the bottom surfaces of the display tiles 100A-D. FIG. 2 shows a cross-sectional view of the tiled display structure illustrated in FIG. 1.
One of the problems with the approach of hiding the seams as described above is that the black matrix or black grid 115 is separated from the pixels by the glass thickness of the display tiles 100A-D. The separation of the black matrix from the pixels by the glass thickness causes some adverse consequences. First, the black matrix acts as an aperture with a size proportional to the ratio of the glass thickness and the pixel pitch. Second, the ability of the black matrix to hide the seams is inversely proportional to the glass thickness. Moreover, the pixel structure leads to a color shift, as the aperture effect selectively impacts the outer read and blue pixels, and is dependent on the viewing angle. These issues associated with the separation of the black matrix from the pixels by the glass thickness can be alleviated by reducing the glass thickness of the display tiles. For example, a 0.2 mm thick front panel can be used for display tiles having 1.75 mm pixel pitch. Glass thickness up to 0.6 mm can give acceptable performance with respect to aperturing, but does not completely obscure the seams. Furthermore, a reduction in pixel pitch will require a proportionate reduction in glass thickness requirements. For instance, a 1.0 mm pixel pitch would require a 0.11 mm thick front panel to meet rigorous display performance requirements or a 0.34 mm thickness to meet more relaxed requirements. In any event, the glass thickness required to ensure good display performance raises substantial issues with respect to manufacturing feasibility, availability, and costs.